Ventilation air and process air distribution for in situ oil shale retorts

A method of ventilating underground workings in a subterranean formation containing oil shale and containing a three-dimensional matrix of underground workings comprising the steps of:

• providing a first airway from above ground to underground workings at an upper level in the formation;
• providing a second airway from above ground to underground workings at a lower level in the formation;
• providing vertical air communication between upper and lower levels remote from the first and second airways:
• withdrawing ventilation air under pressure from the second airway for constantly drawing fresh air from above ground through the first airway, through the upper and lower levels of the underground workings, and through the vertical air communication therebetween;
• and
• withdrawing process off gas under pressure from a plurality of in situ oil shale retorts each having a combustion zone advancing through a fragmented permeable mass of particles containing oil shale, the process off gas being withdrawn at a lower pressure than air pressure in the underground workings at the upper level and lower level, said retorts being in air communication with the underground workings at a level in the formation on the trailing side of such a combustion zone, for constantly drawing fresh air from above ground, through the first airway, and into said in situ retorts.

A method of providing ventilation air for underground workings and process air for a plurality of in situ oil shale retorts in a subterranean formation containing oil shale, each of said retorts containing a fragmented permeable mass of formation particles containing oil shale, the method including the steps of:

• forming a first airway in an upper level of the formation;
• forming a plurality of such in situ oil shale retorts in the formation at an elevation lower than the elevation of the first airway, upper portions of such retorts being in air communication with the first airway;
• forming a second airway in a lower level of the formation;
• providing vertical air communication between the first and second airways;
• forming a gas collection level in fluid communication with lower portions of such in situ oil shale retorts for withdrawing off gas from the retorts;
• withdrawing off gas under pressure from such retorts through the gas collection level at a first gas pressure below ambient air pressure above ground to constantly draw fresh air from above ground through the first airway into such retorts;
• and
• withdrawing air under pressure from the second airway constantly draw fresh air from above ground through the first airway to the underground workings, the fresh air being at a second pressure between ambient air pressure above ground and said first gas pressure.

An air distribution system in a subterranean in situ oil shade formation having underground workings in a retort preparation region of the formation and a plurality of in situ oil shale retorts, in a production region of the formation, each of said retorts containing a fragmented permeable mass of formation particles containing oil shale, the air distribution system comprising:

• an air delivery drift system extending through an upper level of the formation to the retort preparation region and the production region;
• a liquid collection drift system extending through a lower level of the formation to the retort preparation region and the production region for use in removing excavated formation from the retort preparation region and for removing liquid products from the production region;
• a first airway leading between the air delivery drift system and above ground;
• a second airway leading between the liquid collection drift system and above ground;
• at least one vertically extending bypass raise in the retort preparation region in air communication between the air delivery drift system and the liquid collection drift system;
• means for withdrawing air under pressure from the second airway to induce fresh air to flow from above ground through the first airway under a pressure lower than ambient air pressure above ground;
• and circulating a ventilation portin of induced air flow through the air drift system, through such a bypass raise, and through the liquid collection drift system to ventilate the retort preparation region and to remove exhaust ventilation air through the second airway;
• and
• means for withdrawing process off gas under pressure from a plurality of such in situ retorts which are in air communication with the air delivery drift system circulating a process portion of induced fresh air flow through the air drift system to in situ retorts in the production region.

A method of forming an advancing row of in situ oil shale retorts in a subterranean formation containing oil shale comprising the steps of:

• forming an underground air drift at an upper elevation in the formation;
• forming an underground production drift at a lower elevation in said formation vertically spaced apart from the upper air drift;
• forming a first raise between the upper air drift and the lower production drift for providing vertical ventilation air communication between the drifts;
• excavating formation from a portion of the formation adjacent the first raise to form at least one void for forming a first in situ oil shale retort;
• passing excavated formation particles down through the first raise to the lower level production drift;
• forming a second raise between the upper air and lower production drifts beyond the site of said first retort;
• and thereafter excavating formation from a portion of the formation adjacent the second raise to form at least one void for forming a second in situ oil shale retort;
• and
• passing excavated formation particles down through the second raise to the lower level production drift;
• while
• passing ventilation air through the first raise between the upper level air drift and the lower level production drift.

A subterranean in situ oil shale retort system comprising:

• a plurality of in situ oil shale retorts each containing a fragmented permeable mass of formation particles containing oil shale;
• an air delivery drift system in an upper level of the formation at an elevation above such retorts;
• a liquid collection drift system at an elevation below the air delivery drift system for withdrawing excavated formation particles and for withdrawing liquid products from the retorts;
• p1 means for providing ventilation air communication between the air delivery drift system and the liquid collection drift system;
• a gas collection drift system in gas communication with the bottoms of such retorts;
• means for introducing air from the air delivery drift system to the tops of such retorts;
• means for withdrawing process off gas under pressure from such retorts by way of the gas collection drift system at a first pressure below ambient air pressure above ground for drawing process air into such retorts from the air delivery drift system;
• and
• means for withdrawing ventilation air under pressure from the liquid collection drift system at a second pressure between ambient air pressure above ground and the pressure in the gas collection drift system for providing a flow of ventilation air from the air delivery drift system through the means for providing air communication to the liquid collection drift system.

A method of forming an advancing row of in situ oil shale retorts in a subterranean formation containing oil shale, each of said retorts containing a fragmented permeable mass of formation particles containing oil shale, the method comprising the steps of:

• excavating an upper air level drift in the formation;
• excavating a lower production level drift at a lower level in said formation below the air level drift;
• excavating a first raise between the air level drift and the production level drift for providing air communication between the air level and the production level drift;
• excavating a second raise between the air level drift and the production level drift;
• excavating formation particles from within a portion of the formation to become an in situ oil shale retort;
• passing the excavated formation down through the second raise to the production level drift;
• removing excavated formation from the production level drift to above ground;
• and
• introducing ventilation air to the air level drift by withdrawing air under pressure from the production level drift for inducing air flow downwardly through the first raise.